1. Field of the Invention
The present invention relates to a fully enclosed die forging apparatus and more particularly a fully enclosed die forging apparatus provided with a die moving mechanism which has both punches operated to rush into dies, respectively, by moving a die maintained with contact following the movement of a slide toward a punch on a fixed side at a speed slower than the moving speed of the slide.
2. Description of the Prior Art:
Fully enclosed die forging in which raw material is molded in a cavity obtained by having a pair of dies contact with each other is being widely used recently for molding various products because yield of the raw material is high, and moreover, products having complex shapes may be manufactured with high accuracy.
Conventionally, fully enclosed die forging of molded articles 11 represented by a spider of a triport type equal velocity joint for automobiles and so forth having shapes as shown in FIG. 10 and FIG. 11 is performed in such a manner that a cylindrical slug 13 as shown in FIG. 12 is inserted in cavities 19 and 21 formed with an upper die 15 and a lower die 1 as shown in left part of FIG. 13, and upper and lower punches 23 and 25 are made close to each other as shown in the right part of FIG. 13.
Thereupon, when the shape of an aimed forged article 11 is of face symmetric with reference to a cross-section 27 having the maximum area as the forged article 11 described above, it is required to operate upper and lower punches 23 and 25 keeping face symmetry with reference to a cross-section 31 of the maximum area of a cavity 29 while maintaining such a state that above-mentioned upper die 14 and lower die 7 are made to contact with each other and enclosing force is applied.
Because of such reason, a fully enclosed die forging apparatus as shown in FIG. 14 has been used conventionally. For such a fully enclosed die forging apparatus, a hydraulic or mechanical double action press is illustrated, and the left half of the drawing shows the state before forging and the right half of the drawing shows the state after molding, respectively.
In the drawing, reference numeral 11 denotes a forged article, 13 denotes a slug, 15 denotes an upper die, 17 denotes a lower die, 23 denotes an upper punch, 25 denotes a bolster, 35 denotes a bed, 36 denotes an upper pressure pin and 37 denotes a lower pressure pin.
In this full enclosed die forging apparatus, first, the slug 13 is charged by hand or by feeding device into a cavity 38 of the lower die 17. Next, when the slide 33 of the press descends, the upper and lower dies 15 and 17 come into contact with each other. In a hydraulic press, the slide 33 is urged downward by means of a hydraulic device, and in a mechanical press, the slide 33 stops at the bottom dead center, thereby to apply enclosing force to the upper and lower dies 15 and 17.
In succession, in a hydraulic press, a hydraulic unit which is of a different system from the unit for driving the slide 33 installed on the side of the slide 33 and on the side of the bed 35 is operated. In case of a mechanical press, a driving unit installed separately from the unit for driving the slide 33 is operated in the same manner as in the case of the hydraulic press. With this, the upper and lower pressure pins 36 and 37 are operated, the upper and lower punches 23 and 25 are moved toward above-mentioned cross-section 31, and the slug 13 is pushed out for working toward the cavity 29 formed by the upper and lower dies 15 and 17.
Then, after forging, the slide 33 is ascended and the upper and lower dies 15 and 17 are separated. During ascending or at the upper limit thereof, the upper and lower punches 23 and 25 are operated by the hydraulic unit, and the forged article 11 is discharged out of the die.
However, it is required to employ a double action press in order to apply such a fully enclosed die forging apparatus to a hydraulic press. Accordingly, a special purpose machine is required for the forged article 11, which spoils universality. Also, in case of temperature change of pressure oil for operating the upper and lower punches 23 and 25, mixing of bubbles into the pressure oil and so forth are generated, the speed of the upper and lower punches 23 and 25 is changed, which makes it impossible to secure the product accuracy of the forged article 11. In order to avoid this, it has been required to add a correction mechanism which always performs flow control properly.
Besides, in case of application to a mechanical press, a special purpose machine in which a drive unit for driving the upper punch 36 is provided on the side of the slide 33 and a pressure drive unit is also required to be provided on the side of the bed 35 is required. Moreover, because the upper and lower dies 15 and 17 are fitted together at the bottom dead point, enclosing force becomes unstable. Therefore, more enforcing force than required is applied to the press and the upper and lower dies 15 and 17, which makes the life of the metal mold shorter.
The subject applicant has previously applied for patent on a fully enclosed die forging apparatus which is laid open under Provisional Publication No. 133927/84 as a fully enclosed die forging apparatus which is capable of solving such problems.
FIG. 15 shows a fully enclosed die forging apparatus disclosed in said Publication The left half of the Figure shows a state when full enclosing is commenced, and the right half thereof shows the state when forging is completed at the bottom dead point.
In the Figure, an upside die set plate 61 is fixed to a slide 60 of the press, and an insert plate 62 is inserted into this upside die set plate 61 with positioning by a knockout pin 63.
In slide 60, a cushion pin 65 is urged downward by installing a cushion rod 64 which is urged downward by pressure liquid so as to ascend and descend freely. Similarly, a knockout rod 66 is provided in slide 60 so as to ascend and descend freely.
An upside die holder 67 is fixed to the upside die set plate 61, a cam holder 68 is fixed to die holder 67, and furthermore, a first cam 69 is fixed to the cam holder 68. Besides, first cam 69 drives the lower die through a second, a third and a fourth cams which will be described later.
An upper die 70 is fitted to the inside of the upside die holder 67 so as to ascend and descend freely. A punch block 71 and an upper punch 72 are fitted to the inside of this upper die 70 so as to ascend and descend freely.
On the other hand, an underside die set plate 74 is fixed to a bolster 73, and an insert plate 75 is inserted into this die set plate 74. Further, in bolster 73, a knockout rod 76 is provided so as to push up a knockout pin 77 at a constant timing by receiving a pushing-up force by pressure liquid or a mechanical device. In a similar manner, in bolster 73, a cushion pin 79 in the insert plate 75 upward.
To the underside die set plate 74, an underside die holder 80; is positioned and fixed with a knockout pin 81, and a plate 83 is positioned and inserted into this die holder 80 through a knockout pin 82. Further, in underside die holder 80, pads 84 and 85 are built in, and a spring 86 is installed under compressed condition between these pads 84 and 85.
Additionally, this spring 86 urges a lower die, which is described later, upward through a pressure pin 87 penetrating the plate 83 and said pad 84. Inside spring 86, a cushion ring 88 is disposed so as to ascend and descend freely, and the urging force of the cushion pin 79 is arranged so as to be conveyed to a lower die 90 from a pressure pin 89 through this cushion ring 88.
It is also arranged that, at the center of the upper surface of said insert plate 75, a die anvil 92 is provided that penetrates punch block 91 so as to ascend and descend freely, and a lower punch 93 is pushed up with a predetermined timing receiving pushing-up action of a knockout pin 77 by attaching a lower punch 93 on the upper part of the punch block 91.
On the other hand, a guide 95 for guiding a second cam 94, etc. is fixed to said underside die holder 80. This second cam 94 is held by fitting slidably at a bore portion of the guide 95 having a circular form, and the bore portion of this cam 94 is fitted to the lower die 90. A step portion 94a of the cam 94 is engaged with the step portion of the lower die 90, and then cam 94 is held by fitting slidably in a vertical direction only in a guide groove 96 along the center of the die 90.
Further, third and fourth cams 97 and 98 which are held slidably in a circumferential direction only by the lower die 90 and the guide 95 are provided between first cam 69 and second cam 94. Thus, when first cam 69 descends, second cam 94 moves downward through third and fourth cams 97 and 98.
FIG. 16 thru FIG. 18 are drawings showing the locations and operating condition of these cams. As seen from these drawings, two pieces of the first cams 69 are provided at diagonal locations of the cam holder 68 and formed in a cleat shape contracting downward, and the inclined faces of these first cams 69 are made to face between end inclined faces of adjacent third and fourth cams 97 and 98 from the upper part.
Also, the second cam 94 is provided at a location the phase of which is shifted from the first cam 69 by 90.degree. and formed in a cleat shape expanding downward, and by having the inclined surface face between point inclined faces of third and fourth cams 97 and 98 from the lower part, third and fourth cams 97 and 98 are moved in a circumferential direction thereby to push the second cam downward when the first cam 69 descends. Also, the base ends of third and fourth cams 97 and 98 are formed into inclined faces going upward and the point ends are formed into inclined faces going downward.
In a fully enclosed die forging apparatus thus constructed, the slug inserted into the cavity of the lower die 90 is formed under a condition that upper and lower dies 70 and 90 are fully enclosed, and is taken out by the operation of the knockout pin 77, etc.
Thereupon, in this fully enclosed die forging apparatus, at the same time as upper and lower dies come into contact with each other, third and fourth cams 97 and 98 and the first cam 69 contact with each other as shown in FIG. 17. Therefore, when the slide 60 descends and the first cam 69 also descends, adjacent third cam 97 and fourth cam 98 are moved in a horizontal direction, and the second cam 94 which is put between both cams 97 and 98 is pushed downward As the result, the die 90 which is engaged with the second cam 94 descends.
The descending speed of this die 90 is made slower than the descending speed of the punch 72 by setting the angle of each cam face at a predetermined angle, and upper and lower punches 72 and 93 move relatively to upper and lower dies 70 and 90.
In short, despite that upper and lower dies 70 and 90 descend at a lower speed than the descending speed of the upper punch 72, the lower punch 93 does not move. Accordingly, when the slide 60 is made to descend, upper and lower punches 72 and 93 rush into upper and lower dies 70 and 90, respectively, and move closely, thereby to perform expected forging.
In such a conventional fully enclosed die forging apparatus, however, cam 69 of the cam mechanism, which moves upper and lower dies 70 and 90 maintains contact toward the lower punch 93 on the fixed side at a speed lower than the moving speed of the slide 60 and performs rushing operation of upper and lower punches 72 and 93 into upper and lower dies 70 and 90, respectively, is mounted directly on the cam holder 68. Therefore, there is a fear that the cam mechanism is damaged when an abnormal force is applied to the cam mechanism.